Polymerization catalyst comprising an aluminum compound, cobalt salt and ethylene glycol

ABSTRACT

A cobalt/aluminum catalyst for the polymerization of polyesters of terephthalic acid and an ethylene glycol, and a process for the preparation of such catalysts.

FIELD OF THE INVENTION

This is a continuation-in-part of application Ser. No. 08/620,821, filedMar. 25, 1996, now U.S. Pat. No. 5,596,069 which is itself acontinuation-in-part of applications No. 08/487,767, filed Jun. 8, 1995,now U.S. Pat. No. 5,512,340, and of Ser. No. 08/569,044 filed Dec. 7,1995, now abandoned. This invention relates to a catalyst useful for thepreparation of high molecular weight polyester polymers of terephthalicacid and ethylene glycol, to the process for the production of such highmolecular weight polyester polymers, to such high molecular weightpolyester polymers made by the process using the catalyst, and toproducts made from such polyester high molecular weight polymers such asfibers, films, and bottles.

BACKGROUND OF THE INVENTION

Many commercial processes for the production of high molecular weightpolyester polymers of terephthalic acid and ethylene glycol employ anantimony catalyst. The use of an antimony catalyst presents someproblems when the polymer is melt spun into fibers, i.e., the antimonycatalyst residues form deposits around spinneret holes. These depositsmust be wiped off from time to time or the filaments will be defective.It is believed that the antimony deposits form because antimony ispresent in the polymer as antimony glycollate, which boils at about thetemperature of the spinneret. The antimony glycollate vaporizes, andthen hydrolyzes, leaving a non-volatile antimony containing deposit atthe spinneret. A non-antimony containing catalyst is, therefore, adesirable goal.

High molecular weight polyester polymers of terephthalic acid andethylene glycol are usually produced by one of three differentprocesses, namely, (1) the direct esterification and then polymerizationof pure terephthalic acid and ethylene glycol. (This directpolymerization process is satisfactory only if the ingredients are ofhigh purity.) (2) Transesterification of dimethylterephthalate (DMT) andethylene glycol to form, what is called in the art, "DMT monomer." Thetransesterification usually takes place in the presence of a manganese,zinc, or lithium catalyst. The DMT monomer is a mixture of esterproducts (low molecular weight polymer) in which most of the end groupsare glycoxyl, and the mixture contains molecules with a degree ofpolymerization that is 1, 2, or 3. The DMT monomer is then furtherpolymerized to high molecular weight polymer often with an antimonycatalyst. The manganese catalyst used in the transesterificationreaction tends to cause undesirable color in the final product unless itis sequestered; so phosphorus compounds, for example, H₃ PO₄, are oftenadded before the DMT monomer is polymerized to sequester the manganesecatalyst residue. (3) Reaction of medium purity (polymer grade)terephthalic acid and ethylene glycol to form, what is called in theart, "oligomer." The oligomer mixture contains color forming catalystresidues from the manufacture of terephthalic acid. These catalystresidues include manganese, iron, and molybdenum. These catalystresidues are then sequestered by the addition of a phosphoric compound,for example, H₃ PO₄, and then polymerized (polycondensed) to form highmolecular weight polymer. The oligomer has a degree of polymerization ofabout 7, has 500 to 1000 carboxyl end groups per 10 to the 6th powergrams of oligomer. Some cyclic materials are present in the oligomer.(This third process does not require the highly purified startingmaterials necessary for the first process described above.) The catalystof the invention is useful in all three of these processes. In the firstprocess described, the catalyst of the invention may be added at thedirect esterification step or at the beginning of the polymerization; inthe second process described, the catalyst will be added after the DMTmonomer is formed and after the manganese catalyst is sequestered(deactivated); and in the third process the catalyst will be added afterthe color-forming metal impurities in the oligomer are deactivated.

Combinations of metals compounds have been employed in the prior art ascatalyst for the preparation of high molecular weight polymers ofterephthalic acid and ethylene glycols: see, for example, Nichols U.S.Pat. No. 5,116,311; Engle-Bader et al. U.S. Pat. No. 5,166,938; andKosky et al. U.S. Pat. No. 4,590,259.

SUMMARY OF THE INVENTION

The present invention is a polymerization catalyst useful for thepreparation of high molecular weight polymers of terephthalic acid andethylene glycol comprising a cobalt salt and an aluminum compoundselected from the group consisting of aluminum chloride, aluminumhydroxide, aluminum acetate, and aluminum hydroxychloride in ethyleneglycol, where the mole ratio of aluminum to cobalt is 0.25 to 1 to 16 to1, and where the mole ratio of chlorine to aluminum is in the range of 0to 3.

The present invention is also a process for the production ofpoly(ethylene terephthalate) polymer, which comprises combining apolymerization catalyst formed by combining a cobalt salt that issoluble in ethylene glycol and an aluminum compound selected fromaluminum chloride, aluminum hydroxide, aluminum acetate, and aluminumhydroxychloride in ethylene glycol, where the mole ratio of aluminum tocobalt is 0.25 to 1 to 16 to 1, with (a) terephthalic acid and ethyleneglycol, or (b) low molecular weight poly(ethylene terephthalate) polymer(also called DMT monomer), or (c) oligomer, where the concentration ofcobalt in the thus formed mixture is in the range of about 10 to 100parts per million parts of the mixture, and polymerizing the mixture.The aluminum to cobalt mole ratio may be in the range of 1 to 1 to 16 to1 in some circumstances. The optimum aluminum to cobalt mol ratio forgood polymerization and color is about 0.67.

Useful cobalt salts include cobaltous acetate tetrahydrate, cobaltousnitrate, cobaltous chloride, cobalt acetylacetonate, cobalt napthenate,cobalt hydroxide, and cobalt salicyl salicylate. The preferred cobaltsalts are soluble in ethylene glycol in the 100-10,000 parts per millioncobalt range.

This invention is also a process for the preparation of a catalyst forthe preparation of poly(ethylene terephthalate) polymer, which comprisesheating a cobalt salt and an aluminum compound selected from the groupconsisting of aluminum chloride, aluminum hydroxide, aluminum acetate,and aluminum hydroxychloride in ethylene glycol to a temperature in therange of about 40 to 180 degrees C. where the aluminum to cobalt moleratio is in the range of 0.25 to 1 to 16 to 1. A temperature range ofabout 40 to 180 degrees C. is satisfactory: lower temperatures lead toless corrosion of equipment when chloride is present with the aluminumor cobalt salts.

This invention is also a poly(ethylene terephthalate) polymer having aNLRV of greater than about 12 containing catalyst residues of cobalt andaluminum compound, for instance residues of cobalt salt and of aluminumcompound selected from the group consisting of aluminum chloride,aluminum hydroxide, aluminum acetate and aluminum hydroxychloride. Thepolymer can be in the form of a fiber or film or bottle, and may containadditives, as disclosed herein.

This invention is also a process for the production of poly(ethyleneterephthalate) fiber in which there is a reduced need to wipe antimonydeposits from the spinneret face which comprises melt spinning a moltenmixture of poly(ethylene terephthalate) polymer containing catalystresidue of cobalt salt and an aluminum compound as indicated.

DETAILED DESCRIPTION

When the catalyst of the present invention is used to prepare polyesterpolymer from polymer grade terephthalic acid or high purity terephthalicacid, the terephthalic acid (TPA) and ethylene glycol will be fed into areactor. The reaction to form oligomer will proceed without catalyst andis usually conducted at a temperature of about 240 to about 300 degreesC. and at a pressure of about 0 to 50 pounds per square inch. Usually,the reactor will be fed more than an stoichiometric amount of theethylene glycol, and the excess glycol separated by distillation. To theoligomer stream may then be added coloring agents such as carbon black,delustrants, opaquing agents, color, and thermal stabilizers,copolymerization additives such as glycol esters of a metal salt ofdimethyl isophthalate-5-sulfonate, such metal salts being preferablysodium or lithium, isophthalic acid, trimellitic acid and the like.Titanium dioxide is a conventional additive; it serves as a whiteningagent and a delustrant. Most commercial grades of titanium dioxide thatare used in polyester fiber contain antimony compounds which serve asthermal and ultraviolet light stabilizers; so if titanium dioxide isadded to the oligomer, the final product will still contain someantimony, and antimony will show up in the analysis of the polymer. Theantimony in the TiO₂ is chemically bound in the TiO₂ crystal. Sincepolymer grade TPA and plant grade ethylene glycol contain various amountof metals, for example, iron, titanium, molybdenum, cobalt, andmanganese, that tend to give color to the final product, a phosphoruscompound, such as orthophosphoric acid, is often added to TPA/glycolslurry that feeds the direct esterifier or to the oligomer line andmixed to sequester these color forming metal impurities. Then thecatalyst of the present invention is added to the oligomer stream, andthe oligomer is then subjected to polycondensation in the usual manner.

When the catalyst of the present invention is used to prepare polyesterpolymer from dimethylterephthalate (DMT), the DMT and ethylene glycolwill be fed into a reactor along with a transesterification catalyst,for example, manganese, zinc, or lithium acetates, or glycollates. Thereaction that forms DMT monomer is usually conducted at a temperature ofabout 190 to about 260 degrees C. and at a pressure of about 0 to 10pounds per square inch. Sodium, lithium or other metal dimethylisophthalate-5-sulfonate salt may be added with the catalyzed glycol tomake a copolymer. Methanol will be separated by distillation. After thetransesterification, a phosphorus compound such as orthophosphoric acidis added to (deactivate) sequester the ester exchange catalyst, forexample, manganese compound. Then the catalyst of the present inventionis added to the stream, and the DMT monomer subjected topolycondensation in the usual manner. Additives may be incorporated intothe DMT monomer stream, such as fillers, coloring agents, such as carbonblack, delustrants, opaquing agents, color, and thermal stabilizers,copolymerization additives such as glycol esters of a metal salt ofdimethyl isophthalate-5-sulfonate, such metal salts being preferablysodium or lithium, isophthalic acid, trimellitic acid and the like.Titanium dioxide is a conventional additive; it serves as a whiteningagent and a delustrant. Most commercial grades of titanium dioxide usedin polyester fiber contain antimony compounds which serve as thermal andultraviolet light stabilizers; so if titanium dioxide (TiO₂) is added tothe DMT monomer, the final product will still contain some antimony, andantimony will show up in the analysis of the polymer. The antimony inthe TiO₂ is chemically bound in the TiO₂ crystal.

When the catalyst of the present invention is used to prepare polyesterpolymer from pure terephthalic acid, the terephthalic acid (TPA) andethylene glycol will be fed into a reactor. The reaction to formoligomer will proceed without catalyst and is usually conducted at atemperature of about 240 to about 300 degrees C. and at a pressure ofabout 0 to 50 pounds per square inch gauge. Usually, the reactor will befed more than a stoichiometric amount of the ethylene glycol, and theexcess glycol separated by distillation. To the oligomer stream may thenbe added coloring agents, such as carbon black, delustrants, opaquingagents, color, and thermal stabilizers, copolymerization additives suchas glycol esters of a metal salt of dimethyl isophthalate-5-sulfonate,such metal salts being preferably sodium or lithium, isophthalic acid,trimellitic acid, and the like. Titanium dioxide is a conventionaladditive; it serves as a whitening agent and a delustrant. Mostcommercial grades of titanium dioxide used in polyester fiber containantimony compounds which serve as thermal and ultraviolet lightstabilizers; so if titanium dioxide is added to the oligomer, the finalproduct will still contain some antimony, and antimony will show up inthe analysis of the polymer. The antimony in the TiO₂ is chemicallybound in the TiO₂ crystal. Then the catalyst of the present invention isadded to the oligomer stream, and the oligomer subjected topolycondensation in the usual manner.

In order to be a viable replacement for the traditional antimonycatalyst used to polymerize terephthalic acid/ethylene glycol polymers,the desired catalyst should meet the following criteria: 1. It ispreferably soluble in ethylene glycol, but some desirable catalysts maybe in slurry form, such as the reaction product of aluminum hydroxideand cobalt hydroxide. 2. It should produce a polymer which, when formedinto a yarn, has a color, dyeability, and durability about as good asthe yarn made with antimony catalyst. 3. It should be capable of beingused in the same equipment that is presently used for antimony catalyst.4. It should have a reactivity as good as the antimony catalyst. 5. Itshould not deposit on the spinnerets. 6. It should cost about the sameas an antimony catalyst. 7. The catalyst residues should be not betoxic. The catalyst of the invention meets these criteria.

Catalysts of the invention may be prepared as follows:

1. To a 500 cc agitated flasks with reflux condenser add:

0.64 grams of Cobalt diacetate ×4H₂ O dissolved in about 209 grams ofethylene glycol at room temperature.

10.39 grams of Nalco 8676 (aluminum hydroxychloride) is then added withmixing. (Nalco 8676 has an aluminum to chlorine mole ratio of about 0.5.Nalco 8676 is a colloidal suspension in water of aluminumhydroxychloride particles. It is a 10% solution (based on Al₂ O₃) of 20nanometer particles.)

2. Heat 110 to 160 degrees C. and hold about 30 minutes. In ethyleneglycol the solution turns from a pink to a deep purple. Then cool thecatalyst solution. Analyses of the catalyst (Item 3 in the table below)indicated that the chlorine to aluminum mole ratio was about 0.5, andthe aluminum to cobalt mole ratio is about 8 to 1.

Other catalysts were prepared by the above procedure and tabulatedbelow.

    ______________________________________                                        TABLE OF POLYMERIZATION CATALYST SOLUTIONS                                    SAMPLE NO.                                                                            ##STR1## GRAMS CoAc2 × 4H.sub.2 O                                                                    GRAMS OF ETHYLENE GLYCOL                 ______________________________________                                                                    GRAMS                                                                         NALCO 8676                                        1      2         .64        2.57     216.8                                    2      4         .64        5.14     214.2                                    3      8         .64        10.3     209                                      4      16        .64        20.6     198.8                                                                GRAMS OF                                                                      NALCO 8187*                                       5      4         .64        2.6      216.8                                    6      8         .64        5.2      214                                                                  GRAMS OF                                                                      AlCl.sub.3                                        7      2         .64        .686     218.7                                    8      4         .64        1.372    218                                      9      8         .64        2.744    216.6                                    10     16        .64        5.489    213.9                                    ______________________________________                                         *Nalco 8187 is aluminum hydroxychloride solution in water having an           aluminum content measured as Al.sub.2 O.sub.3 of 22% by weight.               (Nalco 8676 and 8187 were analyzed. The percent solids was determined by      drying at 110 degrees C. Nalco 8676 was 21.9 +/- 1.6% solid, and Nalco        8187 was 46.2 +/- .39% solid. When calcined at 900 degrees C., Nalco 8676     was 9.75 +/- .23% solid, and Nalco 8187 was 22.6 +/- .05% solid. The          aluminum content of Nalco 8676 was 5.68% by weight, and the chlorine          content was 3.77%. The aluminum content of Nalco 8187 was 12.4%, and the      chlorine content was 9.3%.)                                              

To make polymer in a 1 liter resin kettle, add 400 grams ofcatalyst-free TPA oligomer. Add 8.6 grams of the catalyst solutions madeper above table to the oligomer with ethylene glycol to make a 2/1 moleratio of ethylene glycol/terephthalate. The total ethylene glycol andcatalyst solution is 129 grams.

It is common commercial practice to vary the composition of polyesterfibers by including, in the mixture to be, polymerized monomers thatimprove the dyeability of fibers made from the polymer. Sodiumisophthalic acid-5-sulfonate glycol ester or trimellitic acid glycolester groups are often incorporated in the polyester chains to improvedyeability. The catalyst of the present invention is compatible withmaking such copolymers.

EXAMPLES Example 1 Lab Resin Kettle Example

Four hundred grams catalyst-free oligomer that was made from pureterephthalic acid and ethylene glycol was combined with 120.4 grams ofethylene glycol and 8.6 grams of ethylene glycol containing thecobalt/aluminum catalyst (#3 in the above table). The amount of catalystwas such that the final polymer contained 14.8 parts per million cobalt,and 54 parts per million aluminum. The mixture was stirred at 60revolutions per minute, heated to 265 degrees C. for 30 minutes, todissolve and remelt the oligomer into the glycol mixture, and thenheated to 275 degrees C. at a pressure of 120 millimeters of mercury andheld at this condition for 20 minutes. The temperature was then raisedto 280 degrees C., and the vacuum adjusted to 30 millimeters of mercuryand held at this condition for 20 minutes. Then the temperature wasraised to 285 degrees, and the pressure lowered to about one (±0.5)millimeters of mercury and held until the agitator torque reached fourpounds per inch at 60 revolutions per minute. Then the agitator speedwas lowered to 40 revolutions per minute, and the torque allowed to riseto 4 pounds per inch. At this point, the polymer was cast in 1/2" widestrips in a pan of cold water. The polymer was then dried andcrystallized at 90 degrees for one hour in a vacuum oven and then groundto pass through a 4 millimeters screen, and then the properties of thepolymer determined. The polymer had an NLRV of 24.19, COOH ends per 10to the 6th power grams of polymer of 26.5, percent of diethylene glycolof 1.208, and a color on the Hunter scale L=74.3, a=-0.5, and b=6.8.(NLRV, a measure of relative viscosity, is the ratio at 25 degrees C. ofthe flow times in a capillary viscometer for the a solution and solvent.The solution is 4.75 wt. percent of polymer in solvent. The solvent ishexafluoroisopropanol.) The polymerization rate was about the same asthat obtained with 200 part per million antimony; the color was close tothat obtained from 200 part per million antimony, and the amount ofdiethylene glycol was somewhat higher than that obtained using 200 partsper million antimony, but still acceptable.

Similar examples with other catalysts prepared, as shown in the "Tableof Polymerization Catalyst Solutions," give similar results to thisExample 1.

Example 2 and Control Examples Semi-Works Example

Control (Antimony Catalyst)

Dimethyl terephthalate (DMT) is fed at 84 pounds per hour to plate 15 ofa 20 plate ester exchange distillation column. Catalyzed glycol was madeby dissolving 590 grams of manganese acetate with 4 waters of hydration,115 grams of sodium acetate, and 853 grams of antimony glycollate atabout 50 degrees C. in 1200 pounds of ethylene glycol. This catalystsolution was fed at 210 milliliters/minute to plate 17 of the esterexchange column. Virgin glycol was fed to the calandria reboiler atabout 70 milliliters/minutes to control the calandria temperature at237±2 degrees C. Glycol boil up in the column was provided by Dowtherm®heat to the calandria's heat exchanger. Methanol was removed from thetop of the column, and methanol reflux was provided to condense theglycol vapor. The monomer produced in the calandria was then pumped andfiltered through a monomer line to the flasher. 13.8 milliliters/minuteof 1% H₃ PO₄ in glycol was added to the monomer line and mixed with themonomer to deactivate the ester exchange manganese catalyst. Then 9.5milliliters/minute of 5% TiO₂ in glycol was injected into the monomerline and mixed with the monomer. The monomer was then prepolymerized ina Dowtherm® heated flashing vessel operated at 245 degrees C. and 90millimeters of mercury pressure. The discharge from the flasher was fedto a Dowtherm® heated, agitated prepolymerization vessel operated at 275degrees C. and 30 millimeters of mercury pressure. The goods from theprepolymerization vessel were then fed to a horizontal screen/wirefilming agitated finishing vessel. This vessel was run at 285 degrees C.and a pressure to produce 19.7±0.6 LRV. (LRV is a measure of relativeviscosity. It is the ratio at 25 degrees C. of the flow times in acapillary viscometer for a solution and a solvent. The solution is 4.75weight percent of polymer in solvent. The solvent ishexafluoroisopropanol containing 100 parts per million H₂ SO₄.) Thepolymer produced was pumped to a spinning machine where yarn was spun at290 degrees C., quenched, and steam drawn to produce a 70 denier 34filament trilobal cross section yarn. This process and productproperties will be compared with product made by use of the catalyst ofthe invention.

Dowtherm® is a registered trademark of the Dow Chemical Co.

Catalyst of the Invention with No Toner

The same process used to prepare the control yarn was used exceptinstead of dissolving antimony glycollate in the catalyzed glycol fed tothe exchanger, the cobalt/aluminum catalyst was prepared separately. 250grams of cobalt acetate with 4 waters of hydration were dissolved in 180pounds of ethylene glycol. 4061 grams of Nalco 8676 was added, and themixture was heated to 160 degrees C. to form a clear purple solution.This catalyst solution was injected into the monomer line at 24milliliters/minute after the 11.4 milliliters/minute of 1% H₃ PO₄solution in glycol was added to deactivate the manganese catalyst.

Catalyst of the Invention with Toner

The catalyst was run the same way as described in the prior paragraphexcept 2 parts per million on a polymer basis of carbozyl violet wasadded with the TiO₂ to change the hue color of the fiber.

                  TABLE                                                           ______________________________________                                        results of the control and invention catalyst runs.                                                w/o                                                                  Control  Toner   With Toner                                       ______________________________________                                        Finisher pressure, mm Hg                                                                    2.96       2.88    3.02                                         % DEG, analyzed                                                                             .9         .83     .87                                          % TiO.sub.2, analyzed                                                                       .096       .097                                                 Sb analyzed, ppm                                                                            240        <1      <1                                           Cobalt added, ppm                                                                           0          24      24                                           Mn, added, ppm                                                                              98         98      98                                           Toner added, ppm                                                                            0          0       2                                            Tenacity, gram/denier                                                                       3.95       3.9     3.95                                         Elongation at break, %                                                                      32         33.4    33.4                                         Boil off shrinkage, %                                                                       8          7.7     7.9                                          Draw tension, grams                                                                         105        104     103                                          (1.2 Draw ratio,                                                              185 degrees C.,                                                               150 yard/minute)                                                              Glf dye       109        108     103                                          Tube color, Hunter lab                                                        L             84.7       83.3    82.3                                         b             1.2        2.5     1.15                                         Color cards, Hunter lab                                                       L             89.4       87.4    87                                           a             -.62       -.38    -.13                                         b             .74        2.10    .76                                          ______________________________________                                    

No visual difference could be seen between control and run with toner.

There was no significant change in spinning filter pack pressure riserate.

Invention and control yarns were judged equal in physical properties.

Invention yarn without toner was less white.

Example 3 Semi -Works

Draw Textured Feed Yarn Example Made with TPA Process

Control Example

Oligomer, with about 7 average degrees of polymerization, was made in acommercial direct esterfier reactor. A side stream was pumped to thesemi-works' flashing vessel, prepolymerizer, and finishing vessels at110 pounds per hour. One item was made with no H₃ PO₄ and one item wasmade with 14 milliliters/minute of 0.1% H₃ PO₄ that was injected intothe oligomer line and mixed with a static mixer to deactivate colorforming metal residues. Then 18.8 milliliters/minute of 1% antimonysolution in ethylene glycol as the polymerization catalyst and 23milliliters/minute of 10% TiO₂, as the delustrant, was then added to theoligomer line and mixed with a static mixer. The polymer was spunthrough a filtration pack and spinneret to produce a 265 denier 34filament draw textured feed yarn, known as partially oriented yarn(POY). This yarn was textured at 700 meters/minute on a Barmag FK-6-900texturing machine.

Invention Example

The invention yarn was made in the same equipment, except 16milliliters/minute of a cobalt aluminum catalyst solution was added tothe oligomer line after the H₃ PO₄ was injected. This catalyst was madeby dissolving 250 grams of cobalt acetate with 4 waters of hydration in180 pounds of ethylene glycol. Then 4061 grams of Nalco 8676 was added.The mixture was then heated with agitation to 170 degrees C. to producea deep blue solution. The solution's theoretical cobalt level is 0.0725%and aluminum level is 0.263%.

Results comparing control and invention product.

    ______________________________________                                                 Control     With    Invention                                                 Without H.sub.3 PO.sub.4                                                                  H.sub.4 PO.sub.4                                                                      With H.sub.3 PO.sub.4                            ______________________________________                                        Finisher pressure                                                                        3.86          2.28    4.94                                         mm Hg                                                                         Sb ppm     228           217     39                                                                            (note 1)                                     TiO.sub.2 %                                                                              .31           .28     .30                                          P ppm      4             9.5     10.1                                                    (from TiO.sub.2)                                                   COOH ends/10 6                                                                           25            26      34                                           grams                                                                         DEG %      1.15          1.12    1.31                                         Yarn properties                                                               Draw tension, grams                                                                      109.5         109     115                                          185 degrees C.                                                                1.71 draw ratio                                                               185 yards/minute                                                              Color on tubes                                                                Hunterlab                                                                     L          84.9          85.7    83.7                                         a          -.3           -.3     .4                                           b          1.9           1.14    .9                                           W          62.8          67.8    65.9                                         color on cards                                                                L          91.0          91.9    90.0                                         a          -1.0          -.85    -.2                                          b          2.55          1.6     1.1                                          W          69.5          76.1    75.3                                         Tenacity,  2.47          2.44    2.43                                         grams/denier                                                                             123.1         121.7   126.8                                        ______________________________________                                         Note:                                                                         1. 9 parts per million antimony comes from the antimony in TiO.sub.2.         About 30 parts per million antimony is in the supply of oligomer.        

Colors of Control and Invention with H3PO4 were judged equivalent byvisual examination.

The textured yarn results show:

    ______________________________________                                                   Control    With                                                               Without H.sub.3 PO.sub.4                                                                 H.sub.3 PO.sub.4                                                                      Invention                                       ______________________________________                                        Tenacity     4.37         4.19    4.21                                        grams/denier                                                                  Elongation % 22.38        21.06   21.17                                       Leesona shrinkage                                                                          18.2         20.0    17.9                                        180 degrees F.                                                                in water, %                                                                   % dye vs. std                                                                              101.1        103.1   102.1                                       equal 100%                                                                    Textured yarn                                                                              .18          .38     0                                           broken filaments                                                              per pound                                                                     ______________________________________                                    

Additional Examples

Similar polymerization experiments for the preparation of poly(ethyleneterephthalate) polymer were carried out using catalyst formed fromcobalt diacetate and aluminum hydroxide in which 0.83 mmoles of cobaltand 0.56 mmoles of aluminum were added to the mixture to be polymerized.The results were highly satisfactory.

Similar polymerization experiments for the preparation of poly(ethyleneterephthalate) polymer were carried out using catalyst formed fromcobalt diacetate and aluminum triacetate in which 0.83 mmoles of cobaltand 0.56 mmoles of aluminum were added to the mixture to be polymerized.The results were highly satisfactory.

Similar polymerization experiments for the preparation of poly(ethyleneterephthalate) polymer were carried out using catalyst formed fromcobalt dihydroxide and aluminum hydroxide in which 0.83 mmoles of cobaltand 0.56 mmoles of aluminum were added to the mixture to be polymerized.The results were highly satisfactory.

Similar polymerization experiments for the preparation of poly(ethyleneterephthalate) polymer were carried out using catalyst formed fromcobalt dihydroxide and aluminum triacetate in which 0.83 mmoles ofcobalt and 0.28 mmoles of aluminum were added to the mixture to bepolymerized. The results were highly satisfactory.

Similar polymerization experiments for the preparation of poly(ethyleneterephthalate(polymer were carried out using catalyst formed from cobaltdiacetate and Nalco 8187 in which 0.84 mmoles of cobalt and 0.58 mmolesof aluminum were added to the mixture to be polymerized. The resultswere highly satisfactory.

What is claimed is:
 1. A polymerization catalyst comprising a cobaltsalt and an aluminum compound selected from the group consisting ofaluminum chloride, aluminum hydroxide, aluminum acetate, and aluminumhydroxychloride in ethylene glycol, where the mole ratio of aluminum tocobalt is in the range of 0.25 to 1 to 16 to 1, and where the mole ratioof chlorine to aluminum is in the range of 0 to
 3. 2. A process for thepreparation of a catalyst for the preparation of poly(ethyleneterephthalate) polymer, which comprises heating a cobalt salt and analuminum compound selected from the group consisting of aluminumchloride, aluminum hydroxide, aluminum acetate, and aluminumhydroxychloride in ethylene glycol to a temperature in the range ofabout 40 to 180 degrees C where the aluminum to cobalt mole ratio is inthe range of 0.25 to 1 to 16 to 1.